Cache poisoning is a type of cyber attack where an attacker manipulates the data stored in a cache, which is a temporary storage area that speeds up data retrieval. By injecting false information into the cache, the attacker can mislead users or systems that rely on that cached data, potentially directing them to malicious websites or providing incorrect information. This technique is often used against Domain Name System (DNS) servers, where attackers alter the cached DNS records. As a result, users may unknowingly access harmful sites instead of the intended ones, leading to data theft or malware infections.